Benthic Ecology Group

Chet takes a break from sample collecting in a seagrass bed.

GCRL's Benthic Ecology Group is directed by Dr. Chet Rakocinski and currently includes seven scientists, graduate students, and technicians. Their work focuses on benthic ecosystems - the aquatic organisms and habitat that reside at the bottom and immediately above it. Benthic organisms form a large part of the food web in our coastal and marine waters.

Former and current projects address estuarine benthic condition, trophic ecology, habitat assessment, and early recruitment dynamics. Much current research activity involves characterizing secondary production on artificial and restored oyster reefs in Mississippi Sound. Mississippi's artificial and oyster reefs make up an important part of the coast's recreational and commercial fisheries. These reefs are currently undergoing substantial rebuilding, restoration, and expansion efforts following Hurricane Katrina and the Deepwater Horizon accident. In addition, marine communities are being challenged by combined multi-stressor effects, including hypoxia and ocean acidification. The Benthic Ecology Group is working to understand the effects of these stressors on the benthic fauna.

Cryptic species are hard to see, either because they are well camouflaged or because they live in crevices or holes or beneath the bottom surface.
Secondary production is the growth of animal biomass in a habitat.

One aspect of their work is characterizing secondary production and the community structure of invertebrates and cryptic fishes on these reefs. Another aspect involves using benthic organisms as indicators of hypoxia, or low oxygen, in sedimentary habitats. Another outgrowth of this effort entails using a modeling approach to reach a mechanistic understanding of effects of hypoxia and organic enrichment on the benthic macroinfauna. The Benthic Ecology Group employs an eclectic and balanced approach, involving a combination of field studies and laboratory experiments in conjunction with simulation modeling.

Lab Members

Kelsey Burns

Ph.D. Student

Kelsey Burns

Kelsey Burns earned a B.S. in 2009 from James Cook University in Townsville, Australia. She worked in Bonaire, Netherland Antilles as a Tropical Marine Ecology Intern before beginning her Ph.D. work at GCRL in 2010.

Kelsey's current research examines the combined effects of hypoxia and temperature on polychaete ecophysiology, including respiration, feeding, and growth.

It is expected that climate change will cause the temperature of the marine environment to rise, and that there will be a greater occurrence and expansion of hypoxia in marine waters of the Gulf of Mexico. (Hypoxia refers to low dissolved oxygen levels in the water, creating an area of limited marine life commonly described as a "dead zone.") Most existing research focuses on how animals respond separately to temperature or hypoxia. Kelsey is going a step further by studying how the combination of these two stressors affects marine life.

Specifically, Kelsey's dissertation will examine the synergistic effects of dissolved oxygen, temperature, and body size on the physiology of the polychaete (worm) Capitella teleta. This will involve observing the respiration, ingestion, egestion, and growth of the polychaete under four levels of dissolved oxygen crossed with three temperatures and the full range of body sizes. Much of the current research looks exclusively at dissolved oxygen, temperature, or body size, but never all three factors at the same time. However, in the natural world, all three factors vary simultaneously, so it is important to understand the possible synergistic (i.e., multiplier) effects of these variables on an animal's physiology, especially during the current era of climate change.

Kelsey stated, “One of my experiments will involve making polychaete feces 'glow' under a black light with the use of a fluorescent DayGlo powder. This will allow me to differentiate between what the animal already had in its stomach and what it eats during the experiments (which will be detritus adulterated with DayGlo powder). This allows me to examine the animal’s feeding without starving it beforehand, which could change the rate of feeding. I am running this experiment to see if polychaetes stop eating under hypoxia when combined with high temperature.”

Kelsey Burns with a beaker containing a mixture of water, materials that polychaetes typically feed on, and DayGlo powder as a dye. The DayGlo powder will allow the food material to be tracked through the worm's digestive system.

Polychaete feces is illuminated with UV light under a microscope. Pellets of feces containing the DayGlo dye mixture fluoresce with a pale yellow-green color, differentiating them from pellets formed from material the animal ate earlier.

Virginia (Ginger) Fleer

Ginger examines fish and small invertebrates collected with a seine on the north side of Horn Island.

Ph.D. Student

Ginger earned her B.S. degree with a double major in Marine Biology and Biological Psychology (pre-med) from Northwest Missouri State University before coming to GCRL in May 2013. Her dissertation work deals with characterizing the trophic (food) relations between fish and benthic invertebrates on restored oyster reefs in the Gulf of Mexico. She is studying predator-prey interactions at the reefs to gain a better understanding of how they might support economically important fish that visit the reefs. Ginger intends to determine whether the limiting effect of hypoxia controls the invertebrate community and fish production or whether the top-down effect of predation by larger reef-associated fish has more impact on the invertebrate and cryptic fish community.

Ginger's work will focus on answering three specific questions.

1.
How does the presence of predators affect the function and structure of the invertebrate community? Hypothesis: There will be a difference in the production and structure of the benthic invertebrate community in experimental predator exclusion units that will provide insights into the trophic dynamics for parameterizing trophic flow models.

2. How does predation by larger reef fish affect cryptic fish and invertebrates, and what bearing does this have on total fish production? Hypothesis: The availability of the habitat refuge for smaller fish will increase their survival rate and growth, thereby enhancing total fish production.

3. How does hypoxia affect trophic structure and function? Hypothesis: The high levels of dredging and nutrient loading combined with climate induced stressors along the coast of the northern Gulf of Mexico will exacerbate hypoxic conditions, decreasing the abundance of benthic organisms and driving away reef-associated fishes; thereby altering trophic functioning of the system and reducing productivity of the reefs.

Claire Matten

Claire is recovering fish traps that have been "soaking" on the bottom of the Mississippi Sound at Katrina Reef for several weeks.

M.S. Student

Claire is from Kingston in London and earned her undergraduate degree in Marine Biology from the University of Wales (Prifysgol Cymru Abertawe) in the U.K. She is in the final stages of completing her M.S. in Coastal Sciences. Immediately before coming to GCRL, Claire spent two years as a port biologist in Seward Alaska for the International Pacific Halibut Commission. Earlier, she had been a field biologist working offshore for the seismic survey industry in the Gulf of Mexico, and as a fisheries observer for CCAMLR (Convention on the Conservation of Antarctic Marine Living Resources) in the Southern Ocean around the island of South Georgia and the South Sandwich Islands.

Claire's M.S. research investigated secondary production on artificial reefs in the Mississippi Sound. Specifically, she studied small cryptic resident fishes on the reefs, and how their condition might be affected by alternative reef designs and materials. The productivity of cryptic fishes on the reefs has implications for organisms at higher trophic levels which feed on small resident fishes. Her work may provide insights into the consequences of using different reef materials and reef designs on the reef community.

Claire's thesis is titled, "Resident Benthic Fishes of Artificial Reefs in the Mississippi Sound: Effects of Habitat Relief and Subregion."

Patrick Gillam

M.S. Student

Patrick is deploying two substrate sample baskets, one rock and one oyster shell, on Katrina Reef south of Deer Island. The samples will remain in the water for six weeks, when they will be retrieved for enumeration of marine organisms, including amphipods, marine worms, and crabs. Major species collected include Eurypanopeus depressus (a mud crab), Alitta succinea (a Nereid worm), Serpulid worms, and Corophium.

Patrick graduated from Presbyterian College in Clinton, South Carolina in 2010 with a B.S. in Biology. He worked as a Biological Science Technician for the U.S. Fish and Wildlife Service at the Orangeburg National Fish Hatchery until 2011.

His current research at GCRL focuses on secondary production and biodiversity of benthic biota on high- and low-profile artificial reefs in the Mississippi Sound. The project also compares two substrate materials: limestone rock and oyster shell. The two high-profile reefs are Katrina Reef in Jackson County and Square Handkerchief Reef in Hancock County. Both reefs were constructed using concrete rubble from nearby bay bridges destroyed by Hurricane Katrina. An examination of the production of benthic organisms on the two materials and two reef types (high vs. low profile) will yield valuable insights into the relative benefits of various artificial reef design and construction alternatives.

A key question associated with artificial reefs is the issue of production vs. attraction. Do the reefs actually produce new fish or do they merely aggregate nearby fish? The current research will help scientists understand the trophic dynamics of the reef and the interactions between the benthos and higher levels in the food web on the reef. When combined with results of studies on other aspects of the reef system at GCRL, Patrick’s study will contribute to a better understanding of how the reefs actually function.

Kathy VanderKooy

Lab Manager and Research Associate

Kathy weighing a rock substrate sample to be placed on an artificial reef in the Mississippi Sound. To extrapolate weight to surface area available for growth of organisms, a sample of individual rocks is weighed individually and then its surface area determined using a laser scanner.

As lab manager, Kathy VanderKooy provides scheduling, data management, and data analysis services for the Lab's research projects, including the artificial reef restoration monitoring project. She is responsible for coordinating field work and sample processing, providing quality control for sample handling by students and technicians, preparation of standard operating procedures (SOPs), purchasing and inventory, and keeping detailed records.

Kathy came to GCRL as student intern in 1988 after earning a B.S. in Biology with an emphasis in marine biology at USM. At GCRL, she completed an M.S. in invertebrate zoology in 1996 under Dr. Richard Heard. She then worked as a technician for two years before taking some time off to raise her children. Kathy joined the Benthic Ecology Group in 2003.

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Scott McIntosh

Technician II

Scott with a flathead catfish, a well-known benthic resident of the Mississippi River.

Scott McIntosh recently joined the Benthic Ecology Group in November 2013. He earned a B.S. in biology and chemistry from the University of Minnesota Duluth. He also worked afterwards with that university to assess Great Lakes coastal wetlands using macroinvertebrates and fishes as bioindicators in relation to land use. Scott arrived at GCRL for his job interview after completing a 2500-mile canoe trip from the origin to the mouth of the Mississippi River.

Read Hendon, director of GCRL's Center for Fisheries Research & Development, positions the boat while Scott McIntosh lowers a substrate sampler tray to be positioned on the bottom by a diver from the Mississippi Department of Marine Resources.